1. Field of the Invention
This invention relates generally to completion and production strings and more particularly to spooled coiled tubing strings having devices and sensors assembled in the string and tested at the surface prior to their deployment in the wellbores.
2. Background of the Art
To obtain hydrocarbons from the earth subsurface formations ("reservoirs") wellbores or boreholes are drilled into the reservoir. The wellbore is completed to flow the hydrocarbons from the reservoirs to the surface through the wellbore. To complete the wellbore, a casing is typically placed in the wellbore. The casing and the wellbore are perforated at desired depths to allow the hydrocarbons to flow from the reservoir to the wellbore. Devices such as sliding sleeves, packers, anchors, fluid flow control devices and a variety of sensors are installed in or on the tubing. Such wellbores are referred to as the "cased holes." For the purpose of this invention, the casing with the associated devices is referred to as the completion string. Additional tubings, flow control devices and sensors are sometimes installed in the casing to control the fluid flow to the surface. Such tubings along with the associated devices are referred to as the "production strings". An electric submersible pump (ESP) is installed in the wellbore to aid the lifting of the hydrocarbons to the surface when the downhole pressure is not sufficient to provide lift to the fluid. Alternatively, the well, at least partially, may be completed without the casing by installing the desired devices and sensors in the uncased well. Such completions are referred to as the "open hole" completions. A string may also be configured to perform the functions of both the completion string and the production string.
Coiled tubing is sometimes used as the tubing for the completion and/or production strings. The coiled tubing is transported to the well site on spools or reels and the devices that cause upsets in the tubing are integrated into the coiled tubing at the well site as it is deployed into the wellbore. Spooled coiled tubing strings with integrated or preamended devices have been proposed. Such strings can be assembled at the factory and deployed in the wellbore without additional assembly at the well site. However, the prior art proposed spooled coiled tubing strings require that there be no "upsets" of the outer diameter of the coiled tubing, i.e., the devices integrated into the coiled tubing must be placed inside the coiled tubing or that their outer surfaces be flush with the outer diameter of the coiled tubing. Such limitations have been considered necessary by the prior art because coiled tubings are inserted and retrieved from the wellbores by injector heads, which are typically designed to handle coiled tubings of uniform outer dimensions. In many oilfield applications, it is not feasible or practical to avoid upsets because the gap between the coiled tubing and the borehole wall or the casing may be too large for efficient use of certain devices such as packers and anchors or because of other design and safety considerations. Also, limiting the outer diameter of the devices to the coiled tubing diameter will require designing new devices.
Additionally, the prior art coiled tubing strings do not include sensors required for determining the operation and health (condition) of the various devices and sensors in the string, or controllers downhole and/or at the surface for operating the downhole devices, for monitoring production from the wellbore and for monitoring the wellbore and reservoir conditions during the life of the wellbore. The prior art spooled coiled tubing strings do not provide mechanisms for testing the devices and sensors from a remote end of the string at the surface before the deployment of such strings in the wellbores. Completely assembling the string with desired devices and sensors and having mechanisms to test the operations of the devices and the sensors at the factory prior to the deployment of the string in the wellbore can substantially increase the quality and reliability of the such strings and reduce the deployment or retrieval time.
The present invention provides spooled coiled tubing strings which include the desired devices and sensors and wherein the devices may cause upsets in the coiled tubing. The string is assembled and tested at the factory and transported to the well site on spools and deployed into the wellbore by a an injector head system designed to accommodate upsets in the tubing strings. The strings of the present invention may be completion strings, production strings and may be deployed in open or cased holes.